Youngster always allowed out (7)
I believe the answer is:
leveret
'youngster' is the definition.
(I've seen this before)
'always allowed out' is the wordplay.
'always' becomes 'ever' (synonyms).
'allowed' becomes 'let' (to let is to allow or permit).
'out' is an insertion indicator.
'ever' put within 'let' is 'LEVERET'.
(Other definitions for leveret that I've seen before include "Young three dn" , "hare about in spring" , "Little beast" , "Baby hare" , "Young creature" .)